groups with websites:

Lancaster EF!
Leeds EF!
London Reclaim the Streets
Manchester EF!
Tyneside Action for People & Planet
also check out www.eco-action.org

and protest camps with websites:
Nine Ladies anti-quarry camp
Faslane Peace Camp
Bilston Glen anti-bypass protest site
Sherwood road protest camp
support groups & publications:
Earth First! Action Update
Do or Die - publication
Blatant Incitement Project - support, advice & resources
Training for Action
Earth First! Gatherings - once or twice a year
Earth Liberation Prisoners support
FreeBeagles - activist legal resources
Activist's Legal Project (useful though some out-of-date)
Activist Security website
UK Action Medics
contacts for groups without websites: contact the EF!AU

and anti-roads camps without websites: take a look at Road Alert! and Weed's pages

and abroad:
for other countries, try the US EF! Journal or www.earthfirst.org.
Also Groen Fronte! (the Netherlands); Zeme Predevsim! (Czech Republic); La Terre d'Abord (Quebec); Australian EF!AU, Melbourne EF! (Australia); Poland EF!; EF! Nigeria; EF! in Italian; EF! Sonora (Mexico); Zem Predovsetkym! (Slovakia); EF! Davao (Phillippines)

"The general principles behind Earth First! are non-hierarchical organisation and the use of direct action to confront, stop and eventually reverse the forces that are responsible for the destruction of the Earth and its inhabitants. EF! is not a cohesive group or campaign, but a convenient banner for people who share similar philosophies to work under."